Auxiliary drive device for the conveying of sheetson a feed table of a cutting press

ABSTRACT

An auxiliary drive device for a machine for processing sheet-like articles. The machine comprises a feed table provided with at least one lower drive belt for transporting a layer of sheet-like articles. A frame of the drive device is arranged above the feed table of the processing machine. The frame supports at least one upper drive belt which cooperates with the lower drive belt(s) for transporting the layer of sheet-like articles by exerting a pressing and driving force on the upper surface of the layer. A mechanism drives the upper belt(s) in synchronism with the lower drive belt(s). A machine for processing sheet-like articles comprises a feed table provided with at least one lower drive belt for transporting a layer of sheet-like articles and comprises such an auxiliary drive device.

The present invention relates to an auxiliary drive device for transporting sheets of paper or cardboard which are arranged in layer form, on the feed table of a cutting press.

In the hitherto known cutting presses, an example of which is shown schematically in FIG. 1, the sheets to be processed are taken from the top of a stack 1, arranged in layer form 3 and then transported on a feed table before being introduced into the grippers 4 of the transportation members 5 of the press cutting station. Thus the document EP1170228 describes an example of a sheet-by-sheet feeding device for arranging said sheets in layer form; and the document EP0680906 describes an example of the transportation member of the press cutting station, which uses gripping bars.

The devices for arranging the sheets in layer form and feeding the layer are shown in greater detail in FIGS. 2 and 3. The stack 1 supplies the layer 3 by means of the suction unit 2, the top of the stack 1 being kept at a constant level owing to raising of the stack-support plate 6 driven by a motor 7. The sheet 8 on top of the stack 1 is gripped at the rear and then pushed forwards by the suction unit 2 so as to form the layer 3, the front part 9 of the sheet 8 being slid underneath the previous sheet 10.

The sheets of the layer 3 are obviously precisely positioned longitudinally and laterally by a positioning device (not shown). The documents EP0669274, EP1044908 and EP1151833 describe examples of the device for positioning the sheets from which the layer 3 is formed. As illustrated in these documents, this positioning operation is performed at one of the ends of the feed table and may be achieved either by means of front and side stops against which the edges of the sheet to be introduced into the press cutting station rest or using a more sophisticated system which does not require stoppage of the sheets.

The feed tables known hitherto generally comprise an inclined platen 12 which may be for example a metal plate or a wooden board which acts as a support for the upper section of at least one drive belt 11. Where several belts 11 are present, they are arranged side-by-side over the width of the inclined surface 12 which therefore supports the upper sections of each of the belts 11.

In order to perform transportation of the sheets of the layer 3 onto the feed table 12, frequently at least one upper auxiliary pressing element 13 is used. The upper auxiliary pressing element(s) 13 is/are mounted on a frame so that it/they can be adjusted positionwise above the upper section of the drive belt or each of the drive belts 11. These auxiliary pressing elements 13 are most often designed in the form of sliding blocks, rollers or small belt conveyors, the pressure of which on the layer 3 of sheets to be transported may sometimes be adjusted. An example of an upper auxiliary pressing element 13 is described in the document EP0684201. When positioning by means of contact against a stop is used, often a rotating brush is used, said brush being positioned so that its bristles give way when the front edge of the first sheet of the layer comes into contact with the stop, thus avoiding damage to the edge of the sheet as a result of an excessively brusque thrusting action by the transportation members.

In the known devices the auxiliary pressing elements 13 only have the function of pressing against the layer 3 so that it is flattened against the upper section of the drive belt or each of the drive belts 11.

The friction is the decisive parameter for the driving force of the layer 3. Moreover the upper section of the drive belt or each drive belt 11 for the sheets project(s) only slightly beyond the surface of the inclined plane 12 so as to ensure correct transportation of low-weight paper.

In the case where the sheets are not composed of flexible material such as low-weight paper or cardboard and moreover have a very slippery surface, the contact between the layer 3 and the upper sections of the belts 11 is no longer sufficient to ensure precise and uniform conveying of the layer 3, as shown in FIG. 5 for a device comprising two drive belts 11. This may occur in particular with sheets of corrugated cardboard which are pasted together. It is thus required to increase significantly the pressing force Fv of the upper auxiliary pressing elements 13, this resulting in some cases in localized crushing of the corrugated cardboard, which is unacceptable nowadays.

The object of the present invention is to overcome the aforementioned drawback so that conveying of the sheets is performed correctly, whatever the material from which they are made, and without damaging them.

To this end, the present invention relates to an auxiliary drive device for a machine for processing sheet-like articles, in accordance with that stated in claim 1, and also to a press for cutting sheet-like articles, in accordance with that stated in claim 7. Claims 2 to 6 define preferred embodiments of the invention.

The invention will be understood better with reference to a preferred embodiment provided by way of a non-limiting example and illustrated by the accompanying drawings in which:

FIG. 1 is a schematic view of an existing cutting press;

FIG. 2 is a schematic view of the different stations of an existing cutting press;

FIGS. 3 and 4 are schematic views of an existing device for arranging the sheets in layer form and for feeding the layer;

FIG. 5 illustrates schematically the problem which is posed in some cases by high-weight sheet-like articles for the existing devices.

FIGS. 6, 7 and 8 show different schematic illustrations of a device according to the invention; and

FIG. 9 shows an embodiment of the driving mechanism of a device according to the invention.

From the point of view of terminology, in order to avoid any confusion in the description which follows, the terms “upstream” and “downstream” will be defined with reference to the direction of displacement of the sheets in layer form. This layer moves from the upstream downstream, along the main axis of the machine. The terms “longitudinal” and “transverse” will also be defined in relation to the main axis of the machine, and the expression “sheet-like articles” is considered to be equivalent to the expression “sheets of paper or cardboard”, this so as to avoid complicating the description by mentioning constructional details which are not directly related to the invention and are well-known to the person skilled in the art.

The invention therefore concerns machines for processing sheet-like articles, of the type comprising a feed table provided with at least one lower drive belt 11 for transporting a layer 3 of sheet-like articles, such as the cutting press shown in FIG. 1 and described above. These machines may reach output speeds ranging from 8,000 sheets per hour to 12,000 sheets per hour when the machine is equipped with a sophisticated positioning device which does not require stoppage of the sheets.

An auxiliary drive device according to the invention is shown in FIG. 6. According to the invention, this device comprises a frame intended to be arranged on top of the feed table of the processing machine. According to the invention, this frame supports at least one upper drive belt 15. If necessary in the example of embodiment of the invention shown in FIG. 6, it supports two of them. The upper drive belts 15 are driven by a shaft 16 in synchronism with the lower drive belt(s) 11.

In the example of embodiment of the invention shown in FIG. 6, the device comprises two movable carriages which may slide on two guide bars 26. Advantageously, and as shown in FIG. 6, one of the carriages is a movable formatting carriage 17 which allows deviation of the upper belt or each upper belt 15 so that it does not rest on top of the layer 3 and only drives the latter as far as the point where the most downstream sheet 14 of the layer 3 is taken up by the positioning device and then the gripper bar 4 of the transportation members 5. The movable formatting carriage 17 therefore allows optimum conveying of the layer 3 whatever the format of the sheets forming it. In the example of embodiment shown in FIG. 6 the movable formatting carriage 17 is the carriage which is situated furthest downstream.

As shown schematically in FIG. 7, this movable carriage comprises at least one transmission pulley 21 allowing formation of an endless belt 15, as well as at least one roller 29 pushed by a resilient member 22 ensuring tensioning of the belt 15.

Optionally, the auxiliary device according to the invention is able to be raised by means of the pivoting of the frame about a shaft 25 situated close to one of its ends. In FIG. 6 the shaft 25 is situated close to the downstream end of the frame, but it is entirely feasible to implement the invention by arranging this shaft close to the upstream end of the frame. When the device is raised, the operator of the processing machine is able to remove easily any sheets which might not be properly separated in the layer 3 or the spacing of which might not be uniform.

Preferably, the device comprises one or more pressure pulleys 20 which exert a pressure on the drive belt 15 and are movable in a direction perpendicular to the surface of the belt 15, so as to be able to be adapted to the thickness of the layer 3 and increase as far as possible the surface area of the layer 3 subject to the pressing and driving force of the belt 15.

A cheek 30 arranged on the movable carriage shown in FIG. 8 supports all the different transmission and pressure pulleys (20, 21, 31, 32). The combination of this set of pulleys, the cheek 30 and the drive belt 15 thus forms a bogie.

Preferably, the device comprises means 23 for adjusting the pressing force exerted by the upper drive belt 15 on the layer 3. These means 23 for adjusting the pressing force may relieve the weight of the device or on the contrary even press onto the layer 3 in addition to the intrinsic weight of the device. In the example of embodiment shown in FIG. 8, the means 23 for adjusting the pressing force consist of a pneumatic jack, the pressure of which may be adjusted. In this example of embodiment of the invention, the bogie is therefore movable. The working position of the bogie is defined by two arms 28 which are hinged at one of their ends on an extension 27 of the movable carriage 17 and hinged at the other of their ends on a shaft, the bogie assembly being also able to pivot about said shaft so as to press the surface of the layer 3 in the best possible manner.

The mechanism for driving the upper drive belt(s) 15 may take different forms, in particular forms involving a mechanical connection of the drive shaft 19 of the lower drive belt(s) 11 to the drive shaft 16 of the upper drive belt(s) 15. FIG. 9 shows an example of embodiment of such a mechanical connection performed by means of two friction wheels 24.

The upper drive belt(s) 15 of the device according to the invention exert a driving force on top of the layer 3, this ensuring correct conveying of the latter whatever the material of the sheet-like articles and without exerting an excessive pressing force. It is thus possible to use a small number of upper drive belts 15, and even decrease the number of lower drive belts 11 of the feed table of the processing machine.

Moreover, the device according to the invention has made it possible to identify and solve another technical problem. In the systems for transporting a layer of sheet-like articles for the feed tables of existing machines, it was noted that there was a slight increase in the speed of the sheet-like articles during transportation thereof, as well as a difference in speed of the articles depending on the thickness of the layer and the number of superimposed articles. This was due to the fact that the pulley for introducing the sheet-like articles onto the feed table has the effect of a side rim. The sheet-like articles were thus slightly accelerated by the sheet-like articles which were slid underneath them and in the end the layer 3 advanced at a speed slightly faster than that of the lower drive belt 11. Moreover the difference in speed between the layer 3 and the belt 11 depended on the number of sheet-like articles stacked within the thickness of the layer and therefore varied between the first article in the layer and the economy speed.

The device according to the invention is able to ensure much more precise transportation than the existing systems owing to synchronization of driving of the upper belts 15 with driving of the lower belts 11. This facilitates management of the sheet-like articles by the positioning device, allowing a better estimation of the position of each sheet-like article within the layer 3 and the moment when the positioning device must take them up.

This problem did not constitute the main problem which the invention proposed to solve a priori, but solving thereof constitutes an additional undeniable advantage of the devices according to the invention compared to the existing devices. 

1. A machine for processing sheet-like articles using an auxiliary drive device, the machine comprising a feed table for feeding of the articles over the table, at least one lower drive belt on a path over the table; for transporting a layer of the sheet-like articles of the auxiliary drive, the auxiliary drive device comprising a frame arranged above the feed table, wherein the frame supports: at least one upper drive belt positioned and operable to cooperate with the lower drive belt(s) and the layer then at the table for transporting the layer of sheet-like articles by exerting a pressing and driving force on an upper surface of the layer; and a drive mechanism operable for driving the upper belt(s) (15) in synchronism with the lower drive belt(s) and against the surfaces of the layer.
 2. The machine of claim 1, wherein the auxiliary drive device comprises a movable carriage movable for formatting the or each upper drive belt.
 3. The machine of claim 1, wherein the auxiliary drive device comprises transmission and pressure pulleys movable in a direction perpendicular to the surface of the or each upper drive belt.
 4. The machine of claim 1, wherein the auxiliary drive device comprises a device operable for adjusting the pressing force exerted by the upper drive belt on the layer.
 5. The machine of claim 4, wherein the device operable for adjusting the pressing force comprise a pneumatic jack.
 6. The machine of claim 1, further comprising a positioning shaft and the device is raised by pivoting of the frame about the shaft.
 7. (canceled) 